Extract Operator

ABSTRACT

In one embodiment, a method includes receiving, from a user, a search query requesting objects of a first object type. The search query includes an inner query requesting objects of a second object type. The method includes identifying objects of the second object type requested by the inner query using an inverted index of a data store corresponding to the second object type; identifying objects of the first object type requested by the search query using the identified objects of the second object type and a forward index of the data store corresponding to the second object type; and sending search results to the user responsive to the search query, each search result corresponding to an identified object of the first object type.

PRIORITY

This application is a continuation under 35 U.S.C. §120 of U.S. patentapplication Ser. No. 13/723,861, filed 21 Dec. 2012.

TECHNICAL FIELD

This disclosure generally relates to a social-networking system.

BACKGROUND

A social-networking system, which may include a social-networkingwebsite, may enable its users (such as persons or organizations) tointeract with it and with each other through it. The social-networkingsystem may, with input from a user, create and store in thesocial-networking system a user profile associated with the user. Theuser profile may include demographic information, communication-channelinformation, and information on personal interests of the user. Thesocial-networking system may also, with input from a user, create andstore a record of relationships of the user with other users of thesocial-networking system, as well as provide services (e.g. wall posts,photo-sharing, event organization, messaging, games, or advertisements)to facilitate social interaction between or among users.

The social-networking system may transmit over one or more networkscontent or messages related to its services to a mobile or othercomputing device of a user. A user may also install softwareapplications on a mobile or other computing device of the user foraccessing a user profile of the user and other data within thesocial-networking system. The social-networking system may generate apersonalized set of content objects to display to a user, such as anewsfeed of aggregated stories of other users connected to the user.

SUMMARY OF PARTICULAR EMBODIMENTS

Particular embodiments may receive a search query requesting firstsearch results of a first object type, while the search query maycomprise an inner query requesting second search results of a secondobject type. Particular embodiments may access an inverted index of adata store corresponding to the second object type, and retrieve thesecond search results requested by the inner query. Particularembodiments may access a forward index of the data store, and retrievethe first search results using the second search results.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example network environment associated with asocial-networking system.

FIG. 2 illustrates an example social graph.

FIG. 3 illustrates an example partitioning for storing objects of asocial-networking system.

FIG. 4 illustrates an example method for searching using a forwardindex.

FIG. 5 illustrates an example computer system.

DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1 illustrates an example network environment 100 associated with asocial-networking system. Network environment 100 includes a user 101, aclient system 130, a social-networking system 160, and a third-partysystem 170 connected to each other by a network 110. Although FIG. 1illustrates a particular arrangement of user 101, client system 130,social-networking system 160, third-party system 170, and network 110,this disclosure contemplates any suitable arrangement of user 101,client system 130, social-networking system 160, third-party system 170,and network 110. As an example and not by way of limitation, two or moreof client system 130, social-networking system 160, and third-partysystem 170 may be connected to each other directly, bypassing network110. As another example, two or more of client system 130,social-networking system 160, and third-party system 170 may bephysically or logically co-located with each other in whole or in part.Moreover, although FIG. 1 illustrates a particular number of users 101,client systems 130, social-networking systems 160, third-party systems170, and networks 110, this disclosure contemplates any suitable numberof users 101, client systems 130, social-networking systems 160,third-party systems 170, and networks 110. As an example and not by wayof limitation, network environment 100 may include multiple users 101,client system 130, social-networking systems 160, third-party systems170, and networks 110.

In particular embodiments, user 101 may be an individual (human user),an entity (e.g., an enterprise, business, or third-party application),or a group (e.g., of individuals or entities) that interacts orcommunicates with or over social-networking system 160. In particularembodiments, social-networking system 160 may be a network-addressablecomputing system hosting an online social network. Social-networkingsystem 160 may generate, store, receive, and transmit social-networkingdata, such as, for example, user-profile data, concept-profile data,social-graph information, or other suitable data related to the onlinesocial network. Social-networking system 160 may be accessed by theother components of network environment 100 either directly or vianetwork 110. In particular embodiments, social-networking system 160 mayinclude an authorization server that allows users 101 to opt in or optout of having their actions logged by social-networking system 160 orshared with other systems (e.g., third-party systems 170), such as, forexample, by setting appropriate privacy settings. In particularembodiments, third-party system 170 may be a network-addressablecomputing system that can host websites or applications. Third-partysystem 170 may generate, store, receive, and transmit third-party systemdata, such as, for example and without limitation, web pages, text,images, video, audio, or applications. Third-party system 170 may beaccessed by the other components of network environment 100 eitherdirectly or via network 110. In particular embodiments, one or moreusers 101 may use one or more client systems 130 to access, send datato, and receive data from social-networking system 160 or third-partysystem 170. Client system 130 may access social-networking system 160 orthird-party system 170 directly, via network 110, or via a third-partysystem. As an example and not by way of limitation, client system 130may access third-party system 170 via social-networking system 160.Client system 130 may be any suitable computing device, such as, forexample, a personal computer, a laptop computer, a cellular telephone, asmartphone, or a tablet computer.

This disclosure contemplates any suitable network 110. As an example andnot by way of limitation, one or more portions of network 110 mayinclude an ad hoc network, an intranet, an extranet, a virtual privatenetwork (VPN), a local area network (LAN), a wireless LAN (WLAN), a widearea network (WAN), a wireless WAN (WWAN), a metropolitan area network(MAN), a portion of the Internet, a portion of the Public SwitchedTelephone Network (PSTN), a cellular telephone network, or a combinationof two or more of these. Network 110 may include one or more networks110.

Links 150 may connect client system 130, social-networking system 160,and third-party system 170 to communication network 110 or to eachother. This disclosure contemplates any suitable links 150. Inparticular embodiments, one or more links 150 include one or morewireline (such as for example Digital Subscriber Line (DSL) or Data OverCable Service Interface Specification (DOCSIS)), wireless (such as forexample Wi-Fi or Worldwide Interoperability for Microwave Access(WiMAX)), or optical (such as for example Synchronous Optical Network(SONET) or Synchronous Digital Hierarchy (SDH)) links. In particularembodiments, one or more links 150 each include an ad hoc network, anintranet, an extranet, a VPN, a LAN, a WLAN, a WAN, a WWAN, a MAN, aportion of the Internet, a portion of the PSTN, a cellulartechnology-based network, a satellite communications technology-basednetwork, another link 150, or a combination of two or more such links150. Links 150 need not necessarily be the same throughout networkenvironment 100. One or more first links 150 may differ in one or morerespects from one or more second links 150.

FIG. 2 illustrates example social graph 200. In particular embodiments,social-networking system 160 may store one or more social graphs 200 inone or more data stores. In particular embodiments, social graph 200 mayinclude multiple nodes—which may include multiple user nodes 202 ormultiple concept nodes 204—and multiple edges 206 connecting the nodes.Example social graph 200 illustrated in FIG. 2 is shown, for didacticpurposes, in a two-dimensional visual map representation. In particularembodiments, a social-networking system 160, client system 130, orthird-party system 170 may access social graph 200 and relatedsocial-graph information for suitable applications. The nodes and edgesof social graph 200 may be stored as data objects, for example, in adata store (such as a social-graph database). Such a data store mayinclude one or more searchable or queryable indexes of nodes or edges ofsocial graph 200.

In particular embodiments, a user node 202 may correspond to a user ofsocial-networking system 160. As an example and not by way oflimitation, a user may be an individual (human user), an entity (e.g.,an enterprise, business, or third-party application), or a group (e.g.,of individuals or entities) that interacts or communicates with or oversocial-networking system 160. In particular embodiments, when a userregisters for an account with social-networking system 160,social-networking system 160 may create a user node 202 corresponding tothe user, and store the user node 202 in one or more data stores. Usersand user nodes 202 described herein may, where appropriate, refer toregistered users and user nodes 202 associated with registered users. Inaddition or as an alternative, users and user nodes 202 described hereinmay, where appropriate, refer to users that have not registered withsocial-networking system 160. In particular embodiments, a user node 202may be associated with information provided by a user or informationgathered by various systems, including social-networking system 160. Asan example and not by way of limitation, a user may provide his or hername, profile picture, contact information, birth date, sex, maritalstatus, family status, employment, education background, preferences,interests, or other demographic information. In particular embodiments,a user node 202 may be associated with one or more data objectscorresponding to information associated with a user. In particularembodiments, a user node 202 may correspond to one or more webpages.

In particular embodiments, a concept node 204 may correspond to aconcept. As an example and not by way of limitation, a concept maycorrespond to a place (such as, for example, a movie theater,restaurant, landmark, or city); a website (such as, for example, awebsite associated with social-network system 160 or a third-partywebsite associated with a web-application server); an entity (such as,for example, a person, business, group, sports team, or celebrity); aresource (such as, for example, an audio file, video file, digitalphoto, text file, structured document, or application) which may belocated within social-networking system 160 or on an external server,such as a web-application server; real or intellectual property (suchas, for example, a sculpture, painting, movie, game, song, idea,photograph, or written work); a game; an activity; an idea or theory;another suitable concept; or two or more such concepts. A concept node204 may be associated with information of a concept provided by a useror information gathered by various systems, including social-networkingsystem 160. As an example and not by way of limitation, information of aconcept may include a name or a title; one or more images (e.g., animage of the cover page of a book); a location (e.g., an address or ageographical location); a website (which may be associated with a URL);contact information (e.g., a phone number or an email address); othersuitable concept information; or any suitable combination of suchinformation. In particular embodiments, a concept node 204 may beassociated with one or more data objects corresponding to informationassociated with concept node 204. In particular embodiments, a conceptnode 204 may correspond to one or more webpages.

In particular embodiments, a node in social graph 200 may represent orbe represented by a webpage (which may be referred to as a “profilepage”). Profile pages may be hosted by or accessible tosocial-networking system 160. Profile pages may also be hosted onthird-party websites associated with a third-party server 170. As anexample and not by way of limitation, a profile page corresponding to aparticular external webpage may be the particular external webpage andthe profile page may correspond to a particular concept node 204.Profile pages may be viewable by all or a selected subset of otherusers. As an example and not by way of limitation, a user node 202 mayhave a corresponding user-profile page in which the corresponding usermay add content, make declarations, or otherwise express himself orherself. As another example and not by way of limitation, a concept node204 may have a corresponding concept-profile page in which one or moreusers may add content, make declarations, or express themselves,particularly in relation to the concept corresponding to concept node204.

In particular embodiments, a concept node 204 may represent athird-party webpage or resource hosted by a third-party system 170. Thethird-party webpage or resource may include, among other elements,content, a selectable or other icon, or other inter-actable object(which may be implemented, for example, in JavaScript, AJAX, or PHPcodes) representing an action or activity. As an example and not by wayof limitation, a third-party webpage may include a selectable icon suchas “like,” “check in,” “eat,” “recommend,” or another suitable action oractivity. A user viewing the third-party webpage may perform an actionby selecting one of the icons (e.g., “eat”), causing a client system 130to transmit to social-networking system 160 a message indicating theuser's action. In response to the message, social-networking system 160may create an edge (e.g., an “eat” edge) between a user node 202corresponding to the user and a concept node 204 corresponding to thethird-party webpage or resource and store edge 206 in one or more datastores.

In particular embodiments, a pair of nodes in social graph 200 may beconnected to each other by one or more edges 206. An edge 206 connectinga pair of nodes may represent a relationship between the pair of nodes.In particular embodiments, an edge 206 may include or represent one ormore data objects or attributes corresponding to the relationshipbetween a pair of nodes. As an example and not by way of limitation, afirst user may indicate that a second user is a “friend” of the firstuser. In response to this indication, social-networking system 160 maytransmit a “friend request” to the second user. If the second userconfirms the “friend request,” social-networking system 160 may createan edge 206 connecting the first user's user node 202 to the seconduser's user node 202 in social graph 200 and store edge 206 associal-graph information in one or more of data stores 24. In theexample of FIG. 2, social graph 200 includes an edge 206 indicating afriend relation between user nodes 202 of user “A” and user “B” and anedge indicating a friend relation between user nodes 202 of user “C” anduser “B.” Although this disclosure describes or illustrates particularedges 206 with particular attributes connecting particular user nodes202, this disclosure contemplates any suitable edges 206 with anysuitable attributes connecting user nodes 202. As an example and not byway of limitation, an edge 206 may represent a friendship, familyrelationship, business or employment relationship, fan relationship,follower relationship, visitor relationship, subscriber relationship,superior/subordinate relationship, reciprocal relationship,non-reciprocal relationship, another suitable type of relationship, ortwo or more such relationships. Moreover, although this disclosuregenerally describes nodes as being connected, this disclosure alsodescribes users or concepts as being connected. Herein, references tousers or concepts being connected may, where appropriate, refer to thenodes corresponding to those users or concepts being connected in socialgraph 200 by one or more edges 206.

In particular embodiments, an edge 206 between a user node 202 and aconcept node 204 may represent a particular action or activity performedby a user associated with user node 202 toward a concept associated witha concept node 204. As an example and not by way of limitation, asillustrated in FIG. 2, a user may “like,” “attended,” “played,”“listened,” “cooked,” “worked at,” or “watched” a concept, each of whichmay correspond to a edge type or subtype. A concept-profile pagecorresponding to a concept node 204 may include, for example, aselectable “check in” icon (such as, for example, a clickable “check in”icon) or a selectable “add to favorites” icon. Similarly, after a userclicks these icons, social-networking system 160 may create a “favorite”edge or a “check in” edge in response to a user's action correspondingto a respective action. As another example and not by way of limitation,a user (user “C”) may listen to a particular song (“Ramble On”) using aparticular application (SPOTIFY, which is an online music application).In this case, social-networking system 160 may create a “listened” edge206 and a “used” edge (as illustrated in FIG. 2) between user nodes 202corresponding to the user and concept nodes 204 corresponding to thesong and application to indicate that the user listened to the song andused the application. Moreover, social-networking system 160 may createa “played” edge 206 (as illustrated in FIG. 2) between concept nodes 204corresponding to the song and the application to indicate that theparticular song was played by the particular application. In this case,“played” edge 206 corresponds to an action performed by an externalapplication (SPOTIFY) on an external audio file (the song “Imagine”).Although this disclosure describes particular edges 206 with particularattributes connecting user nodes 202 and concept nodes 204, thisdisclosure contemplates any suitable edges 206 with any suitableattributes connecting user nodes 202 and concept nodes 204. Moreover,although this disclosure describes edges between a user node 202 and aconcept node 204 representing a single relationship, this disclosurecontemplates edges between a user node 202 and a concept node 204representing one or more relationships. As an example and not by way oflimitation, an edge 206 may represent both that a user likes and hasused at a particular concept. Alternatively, another edge 206 mayrepresent each type of relationship (or multiples of a singlerelationship) between a user node 202 and a concept node 204 (asillustrated in FIG. 2 between user node 202 for user “E” and conceptnode 204 for “SPOTIFY”).

In particular embodiments, social-networking system 160 may create anedge 206 between a user node 202 and a concept node 204 in social graph200. As an example and not by way of limitation, a user viewing aconcept-profile page (such as, for example, by using a web browser or aspecial-purpose application hosted by the user's client system 130) mayindicate that he or she likes the concept represented by the conceptnode 204 by clicking or selecting a “Like” icon, which may cause theuser's client system 130 to transmit to social-networking system 160 amessage indicating the user's liking of the concept associated with theconcept-profile page. In response to the message, social-networkingsystem 160 may create an edge 206 between user node 202 associated withthe user and concept node 204, as illustrated by “like” edge 206 betweenthe user and concept node 204. In particular embodiments,social-networking system 160 may store an edge 206 in one or more datastores. In particular embodiments, an edge 206 may be automaticallyformed by social-networking system 160 in response to a particular useraction. As an example and not by way of limitation, if a first useruploads a picture, watches a movie, or listens to a song, an edge 206may be formed between user node 202 corresponding to the first user andconcept nodes 204 corresponding to those concepts. Although thisdisclosure describes forming particular edges 206 in particular manners,this disclosure contemplates forming any suitable edges 206 in anysuitable manner.

In addition, the degree of separation between any two nodes is definedas the minimum number of hops required to traverse the social graph fromone node to the other. A degree of separation between two nodes can beconsidered a measure of relatedness between the users or the conceptsrepresented by the two nodes in the social graph.

The amount of data (e.g., data for a social graph) stored by asocial-networking system may be very large. For example, a social graphused by Facebook of Menlo Park, Calif. can have a number of nodes in theorder of 10⁸, and a number of edges in the order of 10¹⁰. Typically, alarge collection of data such as a large database may be divided into anumber of partitions. Each partition may be held by separate servers orat separate physical locations. As the index for each partition of adatabase is smaller than the index for the overall database, thepartitioning may improve performance in accessing the database. As thepartitions may be distributed over a large number of servers (while eachpartition may be duplicated at geographically diverse locations), thepartitioning may also improve performance and reliability in accessingthe database. Ordinarily, a database may be partitioned by storing rows(or columns) of the database separately. A database may also bepartitioned by using a hashing algorithm. A database may also bepartitioned by some real-world segmentation of the data held by thedatabase (e.g., customers in each time zone of the United States).Particular embodiments may partition storage of a collection of databased on object types. Particular embodiments may store data objects ina plurality of partitions, each partition holding data objectscorresponding to a single object type.

FIG. 3 illustrates an example partitioning for storing objects of asocial-networking system. In the example of FIG. 3, a plurality of datastores or verticals (e.g., P1, P2, P3, and so on) may store objects of asocial networking system. In particular embodiments, each data store maybe configured to store objects of a particular one of a plurality ofobject types in respective data storage devices 340. Each data store mayalso be configured to store in data storage devices 340 informationassociated with each stored object. An object type may be user, photo,post, web page, or application. Other examples of object types may bemusic, comment, event, message, offer (e.g., coupon), and review. Thisdisclosure contemplates any suitable object types for asocial-networking system.

For example, a user vertical P1 illustrated in FIG. 3 may store userobjects. Each user object stored in the user vertical P1 may comprise anidentifier (e.g., a character string), a user name, and a profilepicture for a user of the social-networking system. Thesocial-networking system may also store in the user vertical P1information associated with a user object such as language, location,education, one or more email addresses, interests, relationship status,a list of friends, a list of family members, privacy settings, and soon. For example, a post vertical P2 illustrated in FIG. 3 may store postobjects. Each post object stored in the post vertical P2 may comprise anidentifier, a text string for a post posted to the social-networkingsystem. The social-networking system may also store in the post verticalP2 information associated with a post object such as a time stamp, anauthor, privacy settings, users who like the post, a count of likes,comments, a count of comments, location, and so on. For example, a photovertical P3 may store photo objects (or objects of other media typessuch as video or audio). Each photo object stored in the photo verticalP3 may comprise an identifier and a photo. The social-networking systemmay also store in the photo vertical P3 information associated with aphoto object such as a time stamp, an author, privacy settings, userswho are tagged in the photo, users who like the photo, comments, and soon.

In particular embodiments, objects stored in each vertical may beindexed by one or more search indices. The search indices may be hostedby respective index server 330 comprising one or more computing devices(e.g., servers). The index server 330 may update the search indicesbased on data (e.g., a photo and information associated with a photo)submitted to the social-networking system by users or other processes ofthe social-networking system (or a third-party system). The index server330 may also update the search indices periodically (e.g., every 24hours). The index server 330 may receive a query comprising a searchterm, and access and retrieve search results from one or more searchindices corresponding to the search term. In some embodiments, avertical corresponding to a particular object type may comprise aplurality of physical or logical partitions, each comprising respectivesearch indices.

In particular embodiments, the search indices for a verticalcorresponding to a first object type may comprise an inverted index. Theinverted index may map a search term associated with a second objecttype to one or more search results of the first object type. Forexample, an inverted index in the post vertical P2 illustrated in FIG. 3may map a search term associated with a user such as(posts_liked_by:<user>) from <user> to a list posts liked by <user>. Theinverted index may map a search term associated with a user such as<posts_commented_by:<user>) from <user> to a list of posts commented by<user>. For example, an inverted index in the photo vertical P3illustrated in FIG. 3 may map a search term associated with a user suchas (photos_liked_by:<user>) from <user> to a list of photos liked by<user>. The inverted index may map a search term associated with a user(photos_tagged_with:<user>) from <user> to a list of photos that <user>is tagged in. In one embodiment, an inverted index for a verticalcorresponding to a particular object type may map a search termassociated with the particular object type to one or more search resultsof the same particular object type. For example, an inverted index inthe user vertical P1 illustrated in FIG. 3 may map a search termassociated with a user such as (friends:<user>) from <user> to a list offriends (i.e., of user object type) of <user>.

In particular embodiments, the search indices for a verticalcorresponding to a first object type may comprise a forward index. Theforward index may map a search term associated with the first objecttype to one or more search results of a second object type. For example,a forward index in the post vertical P2 may map a search term associatedwith a post such as (likers_of:<post>) from <post> to a list of userswho like <post>. The forward index may map a search term associated witha post such as (author_of:<post>) from <post> to a user who is theauthor of <post>. For example, a forward index in the photo vertical P3may map a search term associated with a photo such as(tagged_in:<photo>) from <photo> to a list of users who are tagged in<photo>. The forward index may map a search term associated with a photo(commenters_of:<photo>) from <photo> to a list of users who comment on<photo>. A forward index may comprise a one-to-one mapping for a searchterm. A forward index may also comprise a one-to-few mapping for asearch term. On the other hand, an inverted index may map one to manyfor a search term. For example, a forward index of the photo vertical P3may map a photo to an owner of the photo (e.g., the user who uploadedthe photo to the social-networking system). For example, a forward indexin the photo vertical P3 may map a photo to a few users (e.g., less than10 users) who are tagged in the photo. On the other hand, for example,an inverted index of the photo vertical P3 may map a user to many photos(e.g., more than 100 photos) that the user is tagged in.

Particular embodiments describe methods for efficient search using aforward index. FIG. 4 illustrates an example method 400 for searchingusing a forward index. The method 400 may be implemented by one or morecomputing device (e.g., servers) of the social-networking system. Themethod 400 may begin at step 410. In particular embodiments, at step410, one or more computing devices may receive a search query requestingone or more first search results of a first object type. The searchquery may comprise an inner query requesting one or more second searchresults of a second object type. For example, an aggregator process 320illustrated in FIG. 3 may receive a search query (extract author (termposts_liked by:<9>)). The search query may request (with an extractoperator) a search result in one or more authors for posts that areliked by a user with a user identifier of <9>. The search query mayinclude an inner query (term posts_liked_by:<9>) corresponding to asearch term that requests search results in posts that are liked by theuser <9>. That is, the search query requests a first search result of afirst object type (user), while the inner query requests second searchresults of a second object type (post).

The aggregator process 320 may be one or more computing processes hostedby one or more computing devices (e.g., servers) of thesocial-networking system. For example, the aggregator process 320 maydetermine the search query based on a search request from a PHP(Hypertext Preprocessor) process 310 illustrated in FIG. 3. The PHPprocess 310 may be one or more computing processes hosted by one or morecomputing devices (e.g., servers) of the social-networking system. Thesearch request may be a structured or a substantially unstructured textstring submitted to the PHP process by a user or another process of thesocial-networking system (or a third-party system). For example, theaggregator process 320 may determine the search query (extract author(term posts_liked_by:<9>)) based on a search request “Who are theauthors of the posts I like” submitted to the PHP process 310 by theuser <9>.

In particular embodiments, at step 420, one or more computing devicesmay access an inverted index of a data store corresponding to the secondobject type. In particular embodiments, at step 430, one or morecomputing devices may retrieve the second search results requested bythe inner query using the inverted index of the data store correspondingto the second object type. For example, the aggregator process 320 maysubmit the search query (extract author (term posts_liked_by:<9>))described above to the post vertical P2 illustrated in FIG. 3, causingthe index server 330 of the post vertical P2 to access an inverted indexof the post vertical P2. The inverted index may map a search term(posts_liked_by:<user>) associated with <user> to a list of posts likedby <user>. The index server may access the inverted index and retrieve alist of posts liked by the user <9> as requested by the inner searchquery (term posts_liked_by:<9>). For example, the list of posts liked bythe user <9> may include posts with identifiers <1000>, <2000>, <3000>,<4000>, <5000>, and <6000>.

In particular embodiments, at step 440, one or more computing devicesmay access a forward index of the data store corresponding to the secondobject type. In particular embodiments, at step 450, one or morecomputing device may retrieve the first search results requested by thesearch query using the second search results and the forward index ofthe data store corresponding to the second object type. For example, theindex server of the post vertical P2 described above may access aforward index of the post vertical P2. The forward index may map asearch term (author:<post>) associated with <post> to an author of<post>. The index server may access the forward index (using the extractoperator described earlier) with the result list of posts (<1000>,<2000>, <3000>, <4000>, <5000>, <6000>) for the inner search query (termposts_liked_by:<9>), and retrieve a list of respective authors (e.g.,<31>, <41>, <51>) for the list of posts (<1000>, <2000>, <3000>, <4000>,<5000>, <6000>).

As described earlier, the post vertical P2 may comprise a plurality ofphysical or logical partitions, each comprising respective searchindices. The aggregator process may submit the search query (extractauthor (term posts_liked_by:<9>)) to each partition of the post verticalP2. The index server of each partition may access an inverted index anda forward index of the each partition, and return search results to theaggregator as described above. The aggregator process may then aggregatethe search results from the partitions. For example, a first partitionmay return search results of authors <31> and <51>. A second partitionmay return search results of authors <41> and <51>. The aggregatorprocess may aggregate the results (e.g., by performing an OR operation)yielding an aggregated results of <31>, <41>, and <51>.

With a forward index, the method of FIG. 4 may improve searchperformance as a complex search query (e.g., a query comprising two ormore search queries) may only require accessing one verticalcorresponding to one particular object type. To the contrary, without aforward index, a complex search query may require accessing two or moreverticals, each corresponding to a different particular object type. Asan example, for a complex search query such as searching for authors ofposts liked by the user <9> described above, the aggregator process mayfirst submit first search query (term posts_liked_by:<9>) to the postvertical P2. The index server of the post vertical P2 may access aninverted index of the post vertical P2 (that maps a user to posts likedby the user) with the first search query, and return to the aggregatorprocess a list of posts (e.g., <1000>, <2000>, <3000>, <4000>, <5000>,<6000>) liked by the user <9>. The aggregator process then submit asecond set of search queries (term author:<1000>), (term author:<2000>),(term author:<3000>), and so on, to the user vertical P1. That is,without a forward index in the post vertical P2, the aggregator processmay be required to look up the user vertical P1 not only once butmultiple times. The index server of the user vertical P1 may access aninverted index of the user vertical P1 (that maps a post to its author),and return to the aggregator process a list of authors (e.g., <31>,<41>, <51>) for the list of posts (<1000>, <2000>, <3000>, <4000>,<5000>, <6000>).

In addition, as described earlier, a forward index may indexes searchterms that are one-to-one or one-to-few. Thus a forward index of avertical may be considerably smaller than an inverted index of avertical that may indexes search terms that have one-to-many mappings.The forward index may thus further improve search performance as itssmaller size may improve access and retrieval time for search queries.

In particular embodiments, the aggregator process may rank the firstsearch results by accessing at least another data store corresponding tothe first object type. For example, the aggregator process may submitthe list of authors (<31>, <41>, <51>) described above to the uservertical P1. A server process (hosted by one or more computing devicesof the social-networking system) may rank the authors <31>, <41>, and<51> based on their respective relationship to the user <9> of thesearch query (extract author (term posts_liked_by:<9>)). For example,the server process may rank an author higher if the server processdetermines (e.g., by accessing one or more search indices) that theauthor is a family member of the user <9>. For example, the serverprocess may rank an author higher if the server process determines(e.g., by accessing one or more search indices) that the author has morethan a pre-determined number (e.g., 3) of common interests (or commonfirst-degree friends). The server process may return a ranking orderbetween the authors <31>, <41>, and <51> to the aggregator process.

In other embodiments, one or more computing device (e.g., an indexserver) of the data store corresponding to the second object type mayrank the first search results. For example, the index server of the postvertical P2 may rank the search results of authors <31>, <41>, and <51>described above based on a number of posts in the list of posts liked bythe user <9> (<1000>, <2000>, <3000>, <4000>, <5000>, <6000>) theyauthor. For example, if user <41> authors posts <1000>, <2000>, <3000>,user <31> authors posts <5000> and <6000>, and user <51> authors post<4000>, the index server may rank user <41> as highest as user <41>authors most of the posts in the list of posts liked by the user <9>.The index server may return a ranked search result (<41>, <31>, <51>) asthe first search result to the aggregator process. For another example,the index server may access a forward index that maps a post to a countof likes of the post. The index server may access the forward index andretrieve counts of likes for each post of the list of posts liked by theuser <9>. The index server may rank the posts in the list of posts basedon respective counts of likes, and return to the aggregator processauthors of top ranked posts (e.g., top 3 ranked or most liked posts) asthe first search result.

Particular embodiments may repeat one or more steps of the method ofFIG. 4, where appropriate. Although this disclosure describes andillustrates particular steps of the method of FIG. 4 as occurring in aparticular order, this disclosure contemplates any suitable steps of themethod of FIG. 4 occurring in any suitable order. Moreover, althoughthis disclosure describes and illustrates particular components,devices, or systems carrying out particular steps of the method of FIG.4, this disclosure contemplates any suitable combination of any suitablecomponents, devices, or systems carrying out any suitable steps of themethod of FIG. 4.

FIG. 5 illustrates an example computer system 500. In particularembodiments, one or more computer systems 500 perform one or more stepsof one or more methods described or illustrated herein. In particularembodiments, one or more computer systems 500 provide functionalitydescribed or illustrated herein. In particular embodiments, softwarerunning on one or more computer systems 500 performs one or more stepsof one or more methods described or illustrated herein or providesfunctionality described or illustrated herein. Particular embodimentsinclude one or more portions of one or more computer systems 500.Herein, reference to a computer system may encompass a computing device,and vice versa, where appropriate. Moreover, reference to a computersystem may encompass one or more computer systems, where appropriate.

This disclosure contemplates any suitable number of computer systems500. This disclosure contemplates computer system 500 taking anysuitable physical form. As example and not by way of limitation,computer system 500 may be an embedded computer system, a system-on-chip(SOC), a single-board computer system (SBC) (such as, for example, acomputer-on-module (COM) or system-on-module (SOM)), a desktop computersystem, a laptop or notebook computer system, an interactive kiosk, amainframe, a mesh of computer systems, a mobile telephone, a personaldigital assistant (PDA), a server, a tablet computer system, or acombination of two or more of these. Where appropriate, computer system500 may include one or more computer systems 500; be unitary ordistributed; span multiple locations; span multiple machines; spanmultiple data centers; or reside in a cloud, which may include one ormore cloud components in one or more networks. Where appropriate, one ormore computer systems 500 may perform without substantial spatial ortemporal limitation one or more steps of one or more methods describedor illustrated herein. As an example and not by way of limitation, oneor more computer systems 500 may perform in real time or in batch modeone or more steps of one or more methods described or illustratedherein. One or more computer systems 500 may perform at different timesor at different locations one or more steps of one or more methodsdescribed or illustrated herein, where appropriate.

In particular embodiments, computer system 500 includes a processor 502,memory 504, storage 506, an input/output (I/O) interface 508, acommunication interface 510, and a bus 512. Although this disclosuredescribes and illustrates a particular computer system having aparticular number of particular components in a particular arrangement,this disclosure contemplates any suitable computer system having anysuitable number of any suitable components in any suitable arrangement.

In particular embodiments, processor 502 includes hardware for executinginstructions, such as those making up a computer program. As an exampleand not by way of limitation, to execute instructions, processor 502 mayretrieve (or fetch) the instructions from an internal register, aninternal cache, memory 504, or storage 506; decode and execute them; andthen write one or more results to an internal register, an internalcache, memory 504, or storage 506. In particular embodiments, processor502 may include one or more internal caches for data, instructions, oraddresses. This disclosure contemplates processor 502 including anysuitable number of any suitable internal caches, where appropriate. Asan example and not by way of limitation, processor 502 may include oneor more instruction caches, one or more data caches, and one or moretranslation lookaside buffers (TLBs). Instructions in the instructioncaches may be copies of instructions in memory 504 or storage 506, andthe instruction caches may speed up retrieval of those instructions byprocessor 502. Data in the data caches may be copies of data in memory504 or storage 506 for instructions executing at processor 502 tooperate on; the results of previous instructions executed at processor502 for access by subsequent instructions executing at processor 502 orfor writing to memory 504 or storage 506; or other suitable data. Thedata caches may speed up read or write operations by processor 502. TheTLBs may speed up virtual-address translation for processor 502. Inparticular embodiments, processor 502 may include one or more internalregisters for data, instructions, or addresses. This disclosurecontemplates processor 502 including any suitable number of any suitableinternal registers, where appropriate. Where appropriate, processor 502may include one or more arithmetic logic units (ALUs); be a multi-coreprocessor; or include one or more processors 502. Although thisdisclosure describes and illustrates a particular processor, thisdisclosure contemplates any suitable processor.

In particular embodiments, memory 504 includes main memory for storinginstructions for processor 502 to execute or data for processor 502 tooperate on. As an example and not by way of limitation, computer system500 may load instructions from storage 506 or another source (such as,for example, another computer system 500) to memory 504. Processor 502may then load the instructions from memory 504 to an internal registeror internal cache. To execute the instructions, processor 502 mayretrieve the instructions from the internal register or internal cacheand decode them. During or after execution of the instructions,processor 502 may write one or more results (which may be intermediateor final results) to the internal register or internal cache. Processor502 may then write one or more of those results to memory 504. Inparticular embodiments, processor 502 executes only instructions in oneor more internal registers or internal caches or in memory 504 (asopposed to storage 506 or elsewhere) and operates only on data in one ormore internal registers or internal caches or in memory 504 (as opposedto storage 506 or elsewhere). One or more memory buses (which may eachinclude an address bus and a data bus) may couple processor 502 tomemory 504. Bus 512 may include one or more memory buses, as describedbelow. In particular embodiments, one or more memory management units(MMUs) reside between processor 502 and memory 504 and facilitateaccesses to memory 504 requested by processor 502. In particularembodiments, memory 504 includes random access memory (RAM). This RAMmay be volatile memory, where appropriate Where appropriate, this RAMmay be dynamic RAM (DRAM) or static RAM (SRAM). Moreover, whereappropriate, this RAM may be single-ported or multi-ported RAM. Thisdisclosure contemplates any suitable RAM. Memory 504 may include one ormore memories 504, where appropriate. Although this disclosure describesand illustrates particular memory, this disclosure contemplates anysuitable memory.

In particular embodiments, storage 506 includes mass storage for data orinstructions. As an example and not by way of limitation, storage 506may include a hard disk drive (HDD), a floppy disk drive, flash memory,an optical disc, a magneto-optical disc, magnetic tape, or a UniversalSerial Bus (USB) drive or a combination of two or more of these. Storage506 may include removable or non-removable (or fixed) media, whereappropriate. Storage 506 may be internal or external to computer system500, where appropriate. In particular embodiments, storage 506 isnon-volatile, solid-state memory. In particular embodiments, storage 506includes read-only memory (ROM). Where appropriate, this ROM may bemask-programmed ROM, programmable ROM (PROM), erasable PROM (EPROM),electrically erasable PROM (EEPROM), electrically alterable ROM (EAROM),or flash memory or a combination of two or more of these. Thisdisclosure contemplates mass storage 506 taking any suitable physicalform. Storage 506 may include one or more storage control unitsfacilitating communication between processor 502 and storage 506, whereappropriate. Where appropriate, storage 506 may include one or morestorages 506. Although this disclosure describes and illustratesparticular storage, this disclosure contemplates any suitable storage.

In particular embodiments, I/O interface 508 includes hardware,software, or both, providing one or more interfaces for communicationbetween computer system 500 and one or more I/O devices. Computer system500 may include one or more of these I/O devices, where appropriate. Oneor more of these I/O devices may enable communication between a personand computer system 500. As an example and not by way of limitation, anI/O device may include a keyboard, keypad, microphone, monitor, mouse,printer, scanner, speaker, still camera, stylus, tablet, touch screen,trackball, video camera, another suitable I/O device or a combination oftwo or more of these. An I/O device may include one or more sensors.This disclosure contemplates any suitable I/O devices and any suitableI/O interfaces 508 for them. Where appropriate, I/O interface 508 mayinclude one or more device or software drivers enabling processor 502 todrive one or more of these I/O devices. I/O interface 508 may includeone or more I/O interfaces 508, where appropriate. Although thisdisclosure describes and illustrates a particular I/O interface, thisdisclosure contemplates any suitable I/O interface.

In particular embodiments, communication interface 510 includeshardware, software, or both providing one or more interfaces forcommunication (such as, for example, packet-based communication) betweencomputer system 500 and one or more other computer systems 500 or one ormore networks. As an example and not by way of limitation, communicationinterface 510 may include a network interface controller (NIC) ornetwork adapter for communicating with an Ethernet or other wire-basednetwork or a wireless NIC (WNIC) or wireless adapter for communicatingwith a wireless network, such as a WI-FI network. This disclosurecontemplates any suitable network and any suitable communicationinterface 510 for it. As an example and not by way of limitation,computer system 500 may communicate with an ad hoc network, a personalarea network (PAN), a local area network (LAN), a wide area network(WAN), a metropolitan area network (MAN), or one or more portions of theInternet or a combination of two or more of these. One or more portionsof one or more of these networks may be wired or wireless. As anexample, computer system 500 may communicate with a wireless PAN (WPAN)(such as, for example, a BLUETOOTH WPAN), a WI-FI network, a WI-MAXnetwork, a cellular telephone network (such as, for example, a GlobalSystem for Mobile Communications (GSM) network), or other suitablewireless network or a combination of two or more of these. Computersystem 500 may include any suitable communication interface 510 for anyof these networks, where appropriate. Communication interface 510 mayinclude one or more communication interfaces 510, where appropriate.Although this disclosure describes and illustrates a particularcommunication interface, this disclosure contemplates any suitablecommunication interface.

In particular embodiments, bus 512 includes hardware, software, or bothcoupling components of computer system 500 to each other. As an exampleand not by way of limitation, bus 512 may include an AcceleratedGraphics Port (AGP) or other graphics bus, an Enhanced Industry StandardArchitecture (EISA) bus, a front-side bus (FSB), a HYPERTRANSPORT (HT)interconnect, an Industry Standard Architecture (ISA) bus, an INFINIBANDinterconnect, a low-pin-count (LPC) bus, a memory bus, a Micro ChannelArchitecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, aPCI-Express (PCIe) bus, a serial advanced technology attachment (SATA)bus, a Video Electronics Standards Association local (VLB) bus, oranother suitable bus or a combination of two or more of these. Bus 512may include one or more buses 512, where appropriate. Although thisdisclosure describes and illustrates a particular bus, this disclosurecontemplates any suitable bus or interconnect.

Herein, a computer-readable non-transitory storage medium or media mayinclude one or more semiconductor-based or other integrated circuits(ICs) (such, as for example, field-programmable gate arrays (FPGAs) orapplication-specific ICs (ASICs)), hard disk drives (HDDs), hybrid harddrives (HHDs), optical discs, optical disc drives (ODDs),magneto-optical discs, magneto-optical drives, floppy diskettes, floppydisk drives (FDDs), magnetic tapes, solid-state drives (SSDs),RAM-drives, SECURE DIGITAL cards or drives, any other suitablecomputer-readable non-transitory storage media, or any suitablecombination of two or more of these, where appropriate. Acomputer-readable non-transitory storage medium may be volatile,non-volatile, or a combination of volatile and non-volatile, whereappropriate.

Herein, “or” is inclusive and not exclusive, unless expressly indicatedotherwise or indicated otherwise by context. Therefore, herein, “A or B”means “A, B, or both,” unless expressly indicated otherwise or indicatedotherwise by context. Moreover, “and” is both joint and several, unlessexpressly indicated otherwise or indicated otherwise by context.Therefore, herein, “A and B” means “A and B, jointly or severally,”unless expressly indicated otherwise or indicated otherwise by context.

The scope of this disclosure encompasses all changes, substitutions,variations, alterations, and modifications to the example embodimentsdescribed or illustrated herein that a person having ordinary skill inthe art would comprehend. The scope of this disclosure is not limited tothe example embodiments described or illustrated herein. Moreover,although this disclosure describes and illustrates respectiveembodiments herein as including particular components, elements,functions, operations, or steps, any of these embodiments may includeany combination or permutation of any of the components, elements,functions, operations, or steps described or illustrated anywhere hereinthat a person having ordinary skill in the art would comprehend.Furthermore, reference in the appended claims to an apparatus or systemor a component of an apparatus or system being adapted to, arranged to,capable of, configured to, enabled to, operable to, or operative toperform a particular function encompasses that apparatus, system,component, whether or not it or that particular function is activated,turned on, or unlocked, as long as that apparatus, system, or componentis so adapted, arranged, capable, configured, enabled, operable, oroperative.

What is claimed is:
 1. A method comprising, by one or more computingdevices: receiving, from a client system of a first user of an onlinesocial network, a search query requesting one or more objects of a firstobject type, the search query comprising an inner query requesting oneor more objects of a second object type; identifying the one or moreobjects of the second object type requested by the inner query using aninverted index of a data store corresponding to the second object type;identifying the one or more objects of the first object type requestedby the search query using one or more of the identified objects of thesecond object type and a forward index of the data store correspondingto the second object type; and sending, to the client system of thefirst user, one or more search results responsive to the search query,each search result corresponding to an identified object of the firstobject type.
 2. The method of claim 1, further comprising: accessing asocial graph comprising a plurality of nodes and a plurality of edgesconnecting the nodes, each of the edges between two of the nodesrepresenting a single degree of separation between them, the nodescomprising: a first node corresponding to the first user; and aplurality of second nodes corresponding to a plurality of objectsassociated with the online social network, respectively.
 3. The methodof claim 2, wherein each identified object corresponds to a second nodewithin a threshold degree of separation of the first node within thesocial graph.
 4. The method of claim 1, wherein identifying the one ormore objects of the second type comprises: accessing an inverted indexof a data store corresponding to the second object type, wherein theinverted index maps a user node to one or more concept nodes inaccordance with a second relationship; and retrieving the one or moreobjects of the second object type requested by the inner query using theinverted index of the data store corresponding to the second objecttype, wherein the one or more objects of the second object type compriseone or more concept nodes of a social graph in the social-networkingsystem, and the one or more concept nodes are related, by the secondrelationship, to a user specified in the inner query.
 5. The method ofclaim 1, wherein identifying the one or more objects of the first objecttype comprises: accessing a forward index of the data storecorresponding to the second object type, wherein the forward index mapsa concept node to one or more user nodes in accordance with a firstrelationship; and retrieving the one or more objects of the first objecttype requested by the search query using one or more of the identifiedobjects of the second object type and the forward index of the datastore corresponding to the second object type, wherein the one or moreobjects of the first object type comprise one or more user nodes of thesocial graph that are related to the one or more retrieved concept nodesby the first relationship.
 6. The method of claim 1, wherein the firstobject type corresponds to a user in the online social network and thesecond object type corresponds to a concept in the online socialnetwork.
 7. The method of claim 1, wherein the first or second objecttypes are selected from a group comprising users, posts, photos, videos,audio, web pages, and applications.
 8. The method of claim 1, whereinthe search query is a text string submitted by the first user.
 9. Themethod of claim 1, wherein the search query is a structured orsubstantially unstructured text string.
 10. The method of claim 1,further comprising ranking the one or more search results.
 11. Themethod of claim 10, wherein ranking the one or more search resultscomprises: accessing a data store corresponding to the first objecttype; determining respective relationships of the objects of the firstobject type to an element of the inner query using the data storecorresponding to the first object type; and ranking the one or moresearch results based on the respective relationships of the objects ofthe first object type to the element of the inner query.
 12. The methodof claim 10, wherein the ranking of each search result is based at leastin part on a relationship between the first user and each identifiedobject corresponding to the search result.
 13. The method of claim 10,wherein the ranking of each search result is based at least in part on acount of likes associated with each identified object corresponding tothe search result.
 14. The method of claim 10, wherein the ranking ofeach search result is based at least in part on a number of objectsliked by the first user that are associated with the search result. 15.The method of claim 1, wherein the inverted index maps a search termassociated with the first object type to one or more objects of thesecond object type.
 16. The method of claim 1, wherein the forward indexmaps a search term associated with the second object type to one or moreobjects of the first object type.
 17. The method of claim 1, wherein thesearch query is received by an aggregator process of a social-networkingsystem.
 18. The method of claim 1, wherein the search query is directedto one or more objects within the online social network.
 19. One or morecomputer-readable non-transitory storage media embodying software thatis operable when executed to: receive, from a client system of a firstuser of an online social network, a search query requesting one or moreobjects of a first object type, the search query comprising an innerquery requesting one or more objects of a second object type; identifythe one or more objects of the second object type requested by the innerquery using an inverted index of a data store corresponding to thesecond object type; identify the one or more objects of the first objecttype requested by the search query using one or more of the identifiedobjects of the second object type and a forward index of the data storecorresponding to the second object type; and send, to the client systemof the first user, one or more search results responsive to the searchquery, each search result corresponding to an identified object of thefirst object type.
 20. A system comprising: one or more processors; anda non-transitory memory coupled to the processors comprisinginstructions executable by the processors, the processors operable whenexecuting the instructions to: receive, from a client system of a firstuser of an online social network, a search query requesting one or moreobjects of a first object type, the search query comprising an innerquery requesting one or more objects of a second object type; identifythe one or more objects of the second object type requested by the innerquery using an inverted index of a data store corresponding to thesecond object type; identify the one or more objects of the first objecttype requested by the search query using one or more of the identifiedobjects of the second object type and a forward index of the data storecorresponding to the second object type; and send, to the client systemof the first user, one or more search results responsive to the searchquery, each search result corresponding to an identified object of thefirst object type.